Backflow preventer



FIG. 1 is a front left bottom perspective view of the backflow preventershowing my new design;

FIG. 2 is a front top left perspective view thereof;

FIG. 3 is a front right bottom perspective view thereof;

FIG. 4 is a front top right perspective view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a right side view thereof;

FIG. 8 is a bottom view thereof;

FIG. 9 is a back view thereof; and,

FIG. 10 is a front view thereof.

The broken lines shown in the drawings represent portions of thebackflow preventer that form no part of the claimed design.

CLAIM The ornamental design for a backflow preventer, as shown anddescribed.